Have you heard the phrase "a picture is worth a thousand words"? The distinction between screenplays and novels is this. A script is a visual storyteller; the finished output depicts what is happening in the story - the settings, the characters' activities, and, of course, the language.
The photographs are displayed on a large screen for everyone to view. When writing a novel, the author must describe every element of the plot to construct a picture in the reader's mind using only words - typically describing sentiments and emotions and minute details of the setting. .